Automatic concentration system



May 23, 1933. G. s. VERNAM AUTOMATIC CONCENTRATION SYSTEM Fild Dec. 15, 1951 5 Sheets-Sheet 1 Flour m .N. H J W n m om. mm. L Q m mm.

INVENTOR GILBERT S. VERNAM BY 66/ DDEIEIUI] [II] ATTORN EY SYSTEM Filed Dec. 15, 1931 5 Sheets-Sheet 3 INV ENTOR GILBERT S. VERNAM ATTORNZ Y m QC May 23, 1933.

G. S. VERNAM lg: L

FIG. 4

AUTOMATIC CONCENTRATION SYSTEM INVENTOR GILBERT S. VERNAM 667W ATTOR EY May 23, 1933. G. s. VERNAM AUTOMATIC CONCENTRATION SYSTEM Filed Dec. 15 1931 5 Sheets-Sheet 5 III INVENTOR GILBERT S. VERNAM ATTORN EY Patented May 23, 1933 *UNITEDSTATES PATENT OFFICE GILBERT SQVERNAM, F HAGKENSACK, NEW JERSEY, ASSIGNOR TO INTERNATIONAL COMMUNICATIONS LABORATORIES, INC OE NEWARK, NEW JERSEY, A CORPORA- TION OF NEW YORK AUTOMATIC ooncENrn-Armn SYSTEM Application fiIed Dccember 15,1931.- Serial no. 563L115.

This invention relates generally to printing telegraph exchangesystems and more particularly to such systems in which com-.

bination finder-connector switches are employed for establishinga connection in either direction between subscribers stations and operators sets equipped for both sendingand receiving at a central station.

One of the principalobjects of the present invention is to make it unnecessary for. a central station operator to recall a subscribers station when that station has been calledand found busy.

f Another object is to limit the number of central station operators available to answer incoming calls in accordance with variations in the traffic load. f s

A further object is to insure the operating efliciency of the system by providing alarms that indicate the locationand type of trouble existing anywhere in the system.

In carrying out the objectsof this invention, a busy position locator is provided which serves to indicate to a central station operator, who has called a busy subscribers station, the position of the central station operator in connection withthe busy station, and toindicate to thelatter operator thatthe connection with the subscribersstation is not to be released. The calling operator then re-routes the message for transmission by the connected operator. The busy position locator therefore makesunnecessary repeated attempts. by a central station operator to establish connection with a busy subscribers station. i

To permit the number of central station operators available to answer incoming calls to be varied in accordance with variations in i the traiiic load, a make-busy key associated with each operators position serves, when operated by a supervisor, to make that position busy, and, when released, to make that position idle; while an idle position locator co-operating with the combination finderconnector switches serves to distribute incoming calls to the first idle operators position. A lamp bank associated with these keys indicates to the supervisor whether the corresponding operators positions are busy or ating certain make-busy keys, the supervisor can concentrate incoming calls on predetermined operators positions in accordance with variations in the traflic load. Furthermore,

idle. It is, therefore, evident that b y operin cases where it is desired to have certain central operators positions serve as sending positions only, the supervisor, by operatmg the make-busy keys corresponding to these positions, can concentrate incomingcalls on the remainingpositions.

To permitthe location of trouble that may develop in the system, a number of alarms are provided. One of; these alarms is operated when an incoming call remains unanswered for an abnormal period; another is operated when all of the combination switches are busy; another is operated when all of the combination switches arebusy and an incoming call is waiting;another is opu erated when a comblnatlon switch has been calls on the first idle central station operator.

An additional feature is a combination finder and connector switch having means for preventing the seizure of a busy switch by an idle position locator and also for preventing the seizure of a switch that has not tested a busy subscribers line or is connected to a subscribers line by the busy position cator.

A further feature is the provision of makebusy keys under control of asupervisor for preventing the seizure of any central operators set by the idle position locator as wall as for making any central operators set a sending position only;

Another feature is the provision of the different types of alarms permitting the identification as well as the location of any kind of trouble occurring in the combination switches.

Other objects and features will become apparent when the following description is taken in connection with the" appended claims and with the accompanying drawings, in which:

Fig. 1 illustrates schematically a subscribers station, a combination line finder and connector switch at a centralistation together with a supervisors make-busy key, and the alarms for indicating the existence of trouble in the switches;

Fig. 2 illustrates schematically a central station operators position equipped for both sending and receiving, and additional alarms for indicating trouble in the switch;

Fig. 3 illustrates schematically an idle position locator;

Fig. 4 illustrates schematically a busy position locator;

Fig. 5 illustrates schematically an alternative form of busy position locator in which a lamp bank at the calling operators position is used to indicate which other operator is connected to the busy subscribers line, and

Fig. 6 illustrates the arrangement of the drawings necessary to show the proper relation of the parts of the system. r

In order to afiord a better understanding of the invention, a general description of the system will first be given. Referringto the drawings, a subscribers station V is shown connected by a line circuit 1 to a central station. At the central station there is disclosed a combination finder-connector switch WV, an idle position locator X (Fig. 3), a busy position locator Y (Fig. 4:), and a central station operators set Z. At the central station are disclosed a supervisors position U (Fig. 1), having a make-busy key 1% and a lamp 15 individual to each operators set Z, and alarms S1 (Fig. 1) and S2 (Fig. 2) for indicating the presence of trouble in the system.

Although the parts of the system mentioned have alone been illustrated in the drawings, it is understood that in actual practice, a plurality of subscribers stations, as V;- a plurality of central station operators sets, as Z; a plurality of combination switches, as 1V, suliicient to handle any given number of calls between the subscribers station and the central station operators sets; and a key, as 14, with a lamp, as 15, for each operators set would be provided. Moreover, in asystem containing a large number of subscribers stations, it has been found preferable to employ several idle position locators in order to avoid the excessive use to which a single locator would be subjected in such a system.

A general description otthe operation of the system at this point will probably aid in understanding the detailed desc iption to follow. Assuming first that a call originates at the subscribers station V and that the central station operators set Z is the first idle operators position, the operation of the system in extending a connection from station V to set Z .will be outlined. When the subscribers station V calls, the idle position locator X (Fig. 3), in a system where but one locator is employed, or the first idle position locator having an idle combination switch associated therewith, in a system where several locators are employed, is started. It the idle position locator X isstartcd, it then selects the combination switch after which it causes that switch to be operated until the calling subseribers line 1 is found. Vl hen this occurs the calling subscribers station V and the central station 'operators set Z are interconnected through the switch W. It is to be noted, as mentioned above, that the combination switch 1V is 1ndividual to the central operators set Z, so

that the operation of the switch EV invariably connects the calling subseribers line to the set Z.

. When the switch V] is selected by the idle in readiness to answer the next incoming call.

Likewise, when the switch N finds the calling line, the printer motor at the subscribers station V, which is now connected through the switch VI to the operators set, starts, and the operators printer is now connected in series with. the printer at the subscribers station.

As the printer motor at the set Z is running continuously while the operator is on duty, telegraphic communication between the subscriber and the operators set can now be carried on. At the end of communication, the operator at set Z releases the connection which stops the motor at the subscribers station V. The switch V7 is thereupon released, lamp 58 is extinguished. and the lamp 15 is relighted, indicating to the supervisor that the set Z is again idle.

When the central station operator at set Z desires to establishconnection with the subscribers station. V, he dials the number assigned to this station, and thus operates the associated combination switch W' to establish connection therewith. When the switch W is seized for operation by the operator at set Z the lamp 15 at U is extinguished, inclicating to the supervisor that set Z is busy.

started; The busy positionilocator Y then When ope-rates until it finds the switch W.

this occurs, the busy position locator causes the printer at set Z to be operated to print the number of the operators set in connection with subscribers station V and causes a lamp at the latter operators set tobe lighted,

operators sets cuit, the contacts thus notifying this operator that the connection is not to be released. atorat set Z then releases switch W, which makes switch W selectable by the idle position locator X and extinguishes lamp 15. The calling operator then re-routes the message .fortransmission by the connected operator. Uponthe releaseot switch W the busy position locator Y is prepared to find any other combination switch that hastested a busy subscribers line. a i

It is evident from the foregoing description oi": the operation that the supervisorat U can ascertain which or the central station are busy at any given moment. If the traflic load is such that a portion of the operators sets can handle it, the supervisor, by operating the keys corresponding to the remaining operators sets, can make those sets busy and canthereby concentrate the incoming calls on the first-mentioned sets. Likewise, by operating the corresponding key, the supervisor can convert any set into a sending position only. 9

The description of the various alarms will be deferred until a detailed descriptionof the structure and operation is given.

Referringnow to Fig. 1 the station V is shown connected to the central station by a line circuit 1. At the subscribers station, the line circuit 1extends in series through a low and a high resistance winding of a polar line relay 2, transmitting contacts 1 and printer magnets 3 of the'subscribers printer, and a break key 8 to ground. A printer motor 5, associated with a suitable source oi power, to drive the printer, and a motor control relay 6 controls the op- -rating circuit ofthe motor. The polar line relay 2 is designed so that when negative potential is applied to the line circuit 1, the contacts A of the polar line relay are opened, the motorcontrol relay 6 deenergized, and the printer motor 5 thus stoppedyand when positive potential is appliedto the line cir- A are closed, the motor con trol relay energized, and. the printermotor thereby started, conditioning the printer for the reception or transmission of messages. calling key 7 is also provided, which serves to shunt the high resistance winding of the line relay 2, thus inerca. .'ngthe line current for a purpose to be explainedlater.

At the central station, the line circuit 1 ex- The calling opere subscribers wiper, as

i of switch W, is adapted tends through a line jack9, and a marginal line relay 10 to negative battery. A :printer may be connected to the line jack 9 to handle overflow calls from subscribers station when all of the combination switches, as Vl are busy, or to handle all calls from station .V providing. that station has enough mes sages to keep a single operator busy. Associated with the line relay is a cut-oii relay 11. Similarly, a line and a cut-off relay (not shown) are associated with each of the other subscribers lines (not shown). The line relays are divided into groups of ten, and associated with each group is a group relay 20.

' Associated with the line and group relays is a group of combination finder-connector switches, as 1V, all of which are associated withthe same group of subscribers stations. These switches are similar, in general, to the combination switch disclosed in a 'co-pending application SenNo. 573,323 filed on Novemher 6, 1981 in the name of F. G. Hallden, except that in each switch certain relays have been added, as will be explained later, to control the operation of the busy positio-nlocator Y. Each switch, as W, is individual to a particular central station operators set, as Z, and handles all outward calls from that set and receives inward calls from the subscribers stations as suchcalls are distributed to it by the idle position .locator Each of the switchesis provided with the usual private, line and test terminal banks of contacts and with a vertical commutator. Each vertical commutator and the last level of. each test ter= minal bank is provided with an eleventh or home terminal which serves a purpose that will be described later. The terminal contacts in corresponding banks or the switches are multiplied in the usual manner. private contact 29' of switch W is multiplied by conductor 16 to a terminal contact in the private bank, line contact Z is multipled by conductor 13 to a terminal bank, andtest contact 6 is multipled by conductor 17 to a terminal inthe test bank of each of the other combination switches in the same group. Adapted to be moved over the contacts in the switch, as is a private wiper, as P, adapted to be moved over the contacts in the line bank of each switch, as W, is a line wiper, as L, and adapted to be moved over the contacts in the test bank of each switch, as W, is a test T. The three wipers co-operating with the terminalbanks of ea h switch are mounted on a common shaft (not shown). Also adapted to be moved over the terminals, as r, in the vertical commutator of each switch, as W. is a wiper B.- which is mounted on the same shaft as the other three wipers, P, L and T. The shaft carrying the tour wipers of each switch, as wipers P, L, T and R to he stepped vertically bya vertical magnet, as 19, and rotated Thus private bank of each tacts to an idle position locator, as X by a rotary magnet, as 18, so that the wipers are stepped horizontally. When the shaft is stepped vertically, wiper R moves over the contacts of the vertical commutator while wipers P, L and T are raised to a position adjacent to the first contact of a definite level in their respective banks, and when the shaft rotates, wiper R is raised oil the vertical commutator while wipers P, L and T move over the contacts of this level of their respective banks.

The remainder of the switch structure will be disclosed later.

When line relay 10, associated with subscribers station V is operated, it serves to ground the terminal 6 in the test bank of each of the switches, and also serves to energize the associated group relay 20. When cut-oft relay 11 is energized, it serves to disconnect the line circuit 1 from the line relay 10 and connect it to terminal Z in the line bank of switch W and likewise to the tenninals multipled to Z in the line banks of the other switches. The line and cu -oh relays, associated with each of the other subscribers lines, have similar functions. The group relay 20, when operated, serves to ground the terminal of the vertical commutator in each switch corresponding to the level in which the terminals, associated with the calling su scribers station, appear, and also to close a start leal 11. extending to the idle position locator X. i

As mentioned above, several idle position locators X may, in some instances, be employed: in which case, a group of coinbination switches is associated with each locator. To provide for an extension of the start lead to a subsequent locator when all of the switches are busy in the group associated with a preceding locator, a chain relay, as 21, is associated with each group of switches. When all of the switches in the associated group are busy, the chain relay, as 21, is re leased, and upon its release, the start lead which before extended through its front con- (Fig. 3), is extended through its back contacts to the next idle position locator.

Each idle position locator, as X, includes a rotary switch X1 and a number of control relays for stepping the wipers of the switch X1 and for controlling the combination switch, as W, selected by the idle position locator.

The rotary switch X1 is provided with six contact banks 2227 with each of which cooperates a double ended wiper, as 23-33 mounted on a common shaft 42. Cont .cts as 42A, B, C, etc, in the several terminal banks, 22, 23, 24, etc, are associated with switch TV. Similarly, in each of these terminal hanks there is a contact associated with each one of the other combination switches in the group associated with this idle position locator. The con acts in the several banks associated with the same switch will be hereafter termed a set of contacts corresponding to that switch.

Of the control relays, a relay 38, when initially operated, serves to energize a relay 39 which causes the closure of an initial circuit for a rotary magnet 40, when subsequently operated serves to stop the vertical stepping of a switch selected by the locator X, and, when next operated, serves to stop the horizontal stepping of that switch. ing rotary magnet 40, serves to step the wipers 28-33 as long as the wiper 31 rests on a grounded contact in its associated contact bank 25. As the grounded contacts in this bank are associated with busy combination switches, it is evident that the rotary magnet will step the wipers 28-33 until they rest on a set of contacts associated with the first idle combination switch. A relay 43, which is operated when the wiper 31 reaches an ungrounded contact, serves to disconnect the circuit of the rotary magnet from the wiper 31, and thus prevents the wipers from starting to rotate ag in when the bank contact, now connected with wiper 31, becomes grounded subsequently, as will be explained later. This relay, upon operating, also serves, as will be explained later, to condition the selected switch for operation. A. relay 44: when operated, serves to complete an operating circuit for a relay 4:5, and this last relay is intermittently energized and released, in a manner to be described later, to close and open alternately a pulsing circuit for the selected switch, thus stepping this switch first vertically to select the level in which the terminals of the calling line appear, and then horizontally until the calling line contacts are found. W hen the selected combination switch has found the calling line, the relay 39 is released, and the rotary magnet circuit thus closed through wiper 33. As all but the home contacts in contact bank 27 are grounded, the rotary magnet 1O causes the wipers to step around until wiper 33 rests upon the ungrounded home contact 37 upon which the rotary magnet is de-energized and the wipers brought to rest.

The switch W is provided with the usual pulsing relay 44. When the switch is used as a connector, the relay 4& controls the pulsing circuit of the switch, but when the switch is used as a line finder this relay serves merely to energize an associated slow release relay 45, which, in turn, associates the pulsing circuit extending from the associated idle position locator X with the vertical magnet 19. The vertical magnet 19 serves to step the wipers P, L, T and R of the switch vertically, while the rotary magnet 18 serves to step the wipers horizontally in accordance with the vibrations of the pulsing circuit. Off-normal contacts 47 which operate upon the first vertical step taken by the switch,

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII A self-interrupt-,

slow-release relay .46, associated with the vertical magnet, is released. The vertical magnet 19 and the rotary magnet 18 jointly control a relay 45 in the locator X which, in turn, controls the pulsing circuit for operating the vertical magnet 18 and the rotary magnet .19. Consequently, whenever the pulsing circuit of the switch is closed at the locator X and either the rotary or vertical magnet operated, relay 4:5 is released opening the pulsing circuit and releasing thevertical or rotarymagnet, whichever is operated. The slow-releaserelay 46. also controlsa circuit for operating'relay 38 of the locator X, when the wiper R reaches the grounded terminal in the=vertical commutator, thus opening the pulsing circuit long enough to release both the vertical magnet 19 and the slow-release relay 46, thereby trans ferring the pulsing circuit to the rotary mag net 19. When the rotary magnet 19 has caused the wipers to be brought into con-' nection with the terminals of the calling subscribers lines, the relay 38 in the locator is operated by theground on the test contact t, thus opening the pulsing circuit and stop ping the wipers on these terminals. A relay 51 is provided, which is operated when the wipers of the switch W rest on the terminals of an idle ,subscribers station. Relay 51, upon operating serves to connect the subscribers station, asV, through the switch W, to the central station operators set Z individual with that switch, to open the pulsing circuit of the switch thus preventing any further, stepping of the switch, and to restorethe idle position locator X to its home position uponwhich it isin readiness to answerthe next lncomlng call.

Each switch is also provided w1th relays 50, 52 and53.-When a switch, as W, isbeing used as a connector, relay is operated when the wipers of the switch come to rest on the terminals of a busy subscribers line,

Relay 52, which is responsive'ito the operation of relay 51, serves to complete circuits for notifying the calling central station operator, as Z, that the called subscribefls line is busy, for starting the busyposition locator Y, and for preparing a circuit for operating the relay 53 in the switch connected with the busy subscribers line. When thebusy position locatorY finds the switch W, the wipers. of which are now in contact with theter minals ot'the busy line,;the busy position.

locator causes relay 53 0f the other switch that is already connected withthebusy line tobe operated. That relay, uPOI Operating, completes circuits for notifying the operator in connection with the busy line that the connection is not to be released, and for causing the busy position locator to transmit impulses to the calling operators printer,

sets, as Z, the line circuit normally extends to negative battery through the contacts Aof switching relay 55. This relay, controlled either by the key 54 or by relay 48 of the idle position locator X, serves when operated to connect the line circuit through transmitting contacts 1 56 of the printer and polar line relay 57 to positive battery. The switching relay 55 also controlsa guard lamp 58 which is lighted wheneverthe operators set Z is busy. control relay 59, which is normally held energized by alternative circuits completed at the key 54 and at the associated make-busy key 15, serves to control the operating circuit of the printer. motor 60. Printer magnets 61 of the set printer are connected in the usual local circuit controlled by the polar line relay 57. A holdrelay 62 and a hold lamp63 are connected in a circuit controlledby thebusy position locator Y, while the hold relay, when operated, serves to close a locking circuit for the hold lamp through 1 the contacts of a release key 64. This key likewise controls a locking circuit for the switching relay 55. In addition to the foregoing, a dial 65 for operating switch'W and a resistance shunted busy lamp 66, which is lighted whenever a subscribers line has been tested and found busy, are provided.

At the supervisors position U are located make-busykeys, as 14:, associated with each central. station operators set, as Z, and a lamp, as15, corresponding to ea-ch set, as Z. When the make-busy key correspondingto any set is operated, that set is made busy so that the wipers of the idle'position locator, as X, pass over the set of contacts of the switch associated with that set, and also the control relay, as 59, at that set is placed under control of the set key, as 54:. As previously mentioned, the lamps, as 15, are lighted when the corresponding operators set is idle, and are extinguished when ,that set is, actually busy, or is made busy by the corresponding 1 make-busy key 1 1. 1 c

The busy position locator Y (Fig. 4) comprises a rotaryswitch Y1 and one or more sets of coderelays, as Y2. As previously mentioned, it is the function of the busy position locator Y to respond whenever a called subscribers line is found busy, to set upa local circuitto the calling. operators set and to send over this circuit signals which cause the calling operators printer to record the set number of the operator in connection with the busysubscribers line and also to set up another local circuit from the switch incon nection with the called subscribers station; to the connected operators set which operates a hold lamp notifying this operatorthat' theconnection is not to be released.

The rotary switch Y1 is provided with three terminal banks 67*69. In the drawings, only contacts 70a, 6 and c, are shown associated with one of the combination 5 switches, W, but it is to be understood that in actual practice each of the other combination switches would be similarly provided with a set of contacts, as 70a, 5 and 0, in the terminal banks 67-69. Co-operating with the terminal banks 6769 are double ended wipers 7 072 respectively. These wipers which are mounted on a common shaft 7 3 are adapted to be rotated step-by-step over their associated terminal banks by a self-interrupting magnet 74 which rotates the common shaft 7 3. i

A relay 7 5, which is energized when the start lead of the busy position locator Y is grounded at a combination switch, serves to 0 complete an operating circuit for the rotary magnet 74. This magnet operates intermittently so long as wipers 7 2 rest on a grounded contact in terminal bank 69, thus stepping wipers 7 0-7 2 over the contacts on their associated banks. As will be explained later, the grounded contacts in bank 69 are associated with switches that have not tested a busy subscribers line, while the ungrounded contacts are associated with switches that have tested such lines. relay 76 is provided which operates and releases relay 75 when wiper 72 reaches the first ,ungrounded contact in terminal bank 69. A relay 77, responsive to the closure of the start lead and held operated by relay 7 6., serves to close an operating circuit for a control relay 78, which, upon energizing, connects a suitable source of power to a motor 82. Adapted to be driven by the motor is a shaft (not shown) on which are mounted a plurality of cams (also not shown) each associated with one of the twelve distributor contacts 8394. The cams are so designed that during every revolution each of the eleven distributor contacts 83 and 85- 5 94 are closed once, contacts 83 being closed first and then the remaining contacts 85-94 being closed in sequential order. Contact 84 is closed several times during each revolution in order to transmit certain code signals, as described later.

Associated with the distributor contacts are two groups of code relays, as Y2. The group Y2 includes six relays 95-190. These relays are adapted to be operated 1n various 5 combinations, in accordance with circuits completed by the operation of a relay, as 53, in a combination switch connected with a busy subscribers station. The relays in group Y2 are the tens code relays, and their function is to prepare circuits which are closed at the distributor contacts 85-89 for operating the calling operators printer to record the tens digit of the number designating the set connected to 5 the busy station. Similarly, a group of units code relays (not shown) are provided, and

their function is to prepare circuits closed by the distributor contacts 90-94 for operating the calling operators printer to record the units digit of the number designating the set connected to the busy station.

With two groups of relays as described, any two digit number from 00 to 99 can be recorded. It is obvious, however, that only a single group of code relays would be needed for single digit numbers, and with three or more groups of relays numbers of any size could be recorded.

Inorder to make certain that the motor 82 will accelerate to operating speed before the local circuit from the busy position locator Y is allowed to control the calling operators printer, relays 79-81 and 82 are provided, and the conductor 101, which is extended by the operation of relay 76 to the calling operators printer, is grounded at the contacts A of relay 82, thus making the circuits prepared by the code relays and completed by the closure of the cam controlled distributor contacts inefi'ective to control the calling operators printer until the motor 82 has reached operating speed. The motor is designed to reach operating speed by the time the cam controlling the distributor contacts has made one revolution. Relay 7 9 operates when relay 7 6 pulls up (if the calling operators key is in its normal position, as explained later). Relays 80 and 81 are operated, respectively, upon the first subsequent closure and opening of contacts 88 of the distributor contacts, and relay 130 is operated upon the second closure of these contacts, thus removing the shunting ground and placing the calling operators printer under control of the distributor contacts 8494. As relay 82 is not operated until the second closure of contacts 83, it is evident that the controlling cam has made at least one complete revolution, and thatthe motor 82 has therefore reached operating speed.

The operation of the above-described system in making an outward and an inward call, respectively, will now be described.

Outward call switching relay energizes pulsing relay 44' of combination switch W over a circuit from battery, through low and high resistance windings of relay 44 in series, dial lead 102, lamp 66, dial 65, contacts of switching relay to ground at the release key 64. Relay 44, upon operating, completes an obvious circuit for energizing slow-release relay 45,

which at its F contacts opens the circuit of the operators idle lamp 15, thus extinguishing that lamp which indicates to the super- ,visor at U that operators set Z is busy. The

operation ofrelay 45, in addition to closing other circuits which will be traced later, at its E. contacts grounds contacts 42D 1n term1- nal bank of the idle positionlocator X, thus making the combination switch W busy to incoming calls. r

The operator then dials a two digit number nately opened and closeda predetermined number of times. At each release of relay 44 the verticalmagnet 19 is operated to step the switch mechanism and the wipers P, L, T and B one step vertically, while relays 45 and 46, whichare slow-releasing, rema n cm ergized throughout the series of impulses corresponding to the first dialed digit. The initial circuit for operating relay 46 and vertical magnet 19 may be traced .fI'OIll battery, winding'of verticalmagnet 19, winding of relay 46, contact B of the off-normal contact 47, eleventh rotary contacts 12, contacts B of relay .45, contacts H ofrelay 51, to ground on contacts A of relay 44. Upon the first vertical movement of the switch, the off-non mal contacts 47operate, thus transferring the magnet 19 to the rotary magnet 18. second series of dial pulses operates relay parallel through the windings of relay and the rotarymagnet 18 to battery. The.

' circuit for operating the vertical magnet 19 through contacts B of relay 46 and contacts A of the off-normal contacts, instead of over the previously traced path.

a At the endof the first series of dial pulses the switch W has been stepped vertically to the desired level, and when the dial 65 returns to normal the circuit through the windings of relay44 is closed. Relay 44 comes to rest energized and relay45 is held operated over a circuit through contacts B of relay 44. After a short interval'relay 46 releases, transferringthe pulsing circuit from the vertical The 44 toenergize the rotary magnet 18 intermittently over a circuitwhich extends from ground through contacts Aof relay 44, con tacts H of relay 51, contacts B of relay 45,

, oil-normal contacts A, contacts A of relay 46, contacts D of relay50, and in parallel through winding of slow-release relay 48 and through windingof rotary magnet. 18 to battery. Upon the first closure of this circuit relay 48 pulls up, transferring the V66 pulsing circuit through its D contacts and in second series of dial pulses causes the switch I mechanism and the wipers P, L and T tobe stepped in the rotary direction to the proper bank terminals of the previously selected level. While the switch W is being stepped by the rotary magnet 18, relay 48, being of the slow-release type, remains operated.

When the switch wipers P, L and T come I to rest on the selected bank terminals and for a short time thereafter (while relay 48 remains operated), a circuit is extended from the p bank terminal, wiperiP, contactsC of relay 48 through the winding of relay 50 and to battery. If the called subscribers line is idle the circuit from the ;0 bank terminal ex tends to battery. through the winding of cutoff relay 11. In this case relay 50 cannot operate. After a short interval of time relay Q 48 releases and establishes a circuit from but tery through the winding of cut-off relay 11, p bank terminal, wiper P, contacts B of.

relay 48, lower winding of relay 51, contacts A ofrelay 50, contacts C of relay 45 to ground.

Cut-off relay 11 operates and the lower winding of relay 51 is energized to close only contacts D. Closure of contacts D of relay 51 establishes a circuit from battery through plained in detail later, relay 104 controls an 1' alarm for indicatingthe failure of the combination switch W to complete its operation. The opening of contacts B opens a circuit through chain relay 21. As the operating circuit of relay 21 is multipled by conductor 105to similar contacts of an identical relay in other combination switches of the same group,'this relay remains operated unless all of the other switches are also busy. The closure of contacts C completes an obvious locking circuit for the cut-ofi relay 11. The closure of contacts E connects the L wiper through tothe operators set'Z over a circuit to be'traced later. The closure of contacts F connects relay 53 to the test wiper T'. The opening of contacts G opens a connection extending tocontacts A of the relay 52. The

opening of contacts H opens the pulsingcir cuit from contacts A of relay 44, thus making any further dial pulses ineffective on the switch W.

The line circuit may now be traced from ground. at the subscribers station through the break key 8, printer magnet 3, keyboard 4, both win-dings of the polar line relay 2, line 1, line .j ack contacts 9, contacts A of cutoff relay 11 (now energized), bank terminal Z, and wiper L,contacts E of relay 51, line lead 106to operators set Z, contacts B of the switching relay 55, contactsE of the operators key 54, to'negative battery. It may be noted at this point that, previous to the operation of cut-H relay 11, the line circuit extended to negative battery through the winding of line relay 10. As previously mentioned, the polar line relay Z at the subscribers station V is so designed that negative potential will hold its contacts A open, and hence the establishment of a connection from the operators set Z to the subscribers station set V has in itself no effect on the station equipment.

After dialling the two digits to select the subscribers station V, the operators' key 54 is restored to the center position. Under this condition the line circuit 106 at the operators set Z extends from the contacts B of the switching relay 55 through the keyboard contacts 56, contacts C of operators key 54, winding of polar relay 5?, contacts of the operated control relay 59 to positive battery. Upon this reversal of current in the line circuit 1, the polar line relay 2 at the subscribers station V now operates to close its A contacts, thus establishing a circuit from one pole of a power source through the winding of the mocr control relay 0 to the other pole of the power source. The control relay operates to close an obvious circuit through the station printer motor 5 and to close another obvious circuit which shunts out the high resistance winding of the polar line relay 2. Removal of this high resistance winding from the line circuit 1 raises the line current from the idle condition value to a value suitable for telegraphic communication. 7 H

A connection is now completed from the operators set printer at the central oflice through the finder-connector switch W to the selected subscribers station printer. The station motor 5 has been started and, as the printer motor 60 at set Z runs continuously, telegraphic communication can now be carried on between the central station operators set Z and the subscribers station V.

It should be noted that several provisionsare made in the circuit to prevent faulty operation, and particularly to prevent the central station operator from sending a message which, because of some false operation or failure of the lines or equipment, is not received by the called subscribers printer. If, after dialling, the central station operator should attempt to send without first restoring her key 54 to the center position, she will be warned by the fact that the message is not recorded on her own printer, as under this condition the keyboard 56 is disconnected from the line circuit 100 at contacts C of the key 54. On the other hand, if the key 54 is restored properly, the central station operators printer set is connected to the line lead 106 which is now closed through the selected subscribers line 1 to ground at the subscrib- 65. ers station Y. If the central station operator should dial a spare line, if the switch should fail to cut through to a working line, if the outside line should be open, if the polar line relay 2 at the subscribers station V should fail to function, if failure of thelocal power supply at station V, or other cause, should prevent the operation of control relay 6 and the high resistance winding of the polar line relay 2 should thus remain in the line circuit 1, the latter circuit is left open or the line current is so reduced that the operators printer at Z acts as though connected to an open line and no record of the messagewill be made by that printer. This serves as an indication to the central station operator that connection has not been established with the called subscribers printer.

After the message has been transmitted, the central office operator may release the con nection by operating the release key 64. The operation of this key opens the circuit of the guard lamp 58 and removes locking ground from the winding of the switching relay 55 so that this relay releases, thus applying negative battery to the line lead 100, operating the polar line relay 2 at the station V and restoring the station circuits to normal. Ground is also removed from the dial lead 102 extending to the windings of relay 44, so that this relay releases. The release of relay 44 opens the circuit of relay 45 which releases. The release of relay 45 opens the circuit through the upper winding of relay 51, whereupon this relay releases to restore to normal the circuits previously traced through its contacts. The release of relays 45 and 51 establishes a circuit from the ground on contacts A of relay 44, contacts H of relay 51, contacts A of relay 45, err-normal contacts C, winding of release magnet 49, winding of relay 107 (Fig. 2) to battery. The release magnet 49 thereupon operates over the circuit traced, restoring the switch mechanism to normal, at which time the off-normal contacts 47 open to de-energize the release magnet 49. Release of relay 45 also removes ground from the bank terminal 421) of the idle position selector switch X and connects this ground to the operators idle lamp 15 individual to switch WV. lhe switch WV is now in condition to receive inward calls and the operators idle lamp 15 is lighted to inform the supervisor that the position is idle.

If, because of some mechanical defect, the release function of the switch W is not completed, the circuit through the release magnet 49 and the winding of relay 10'? (Fig. 2) is maintained through contacts 0 of the off-normal springs 4?. Relay 107 is then held operated to maintain an obvious circuit through the winding ofa dash-pot relay 108. After a predetermined interval dash-pot relay 108 operates, causing a green lamp 109 to light and bell 110 to ring. The attendant is thus informed by the hell that a switch is in trouble, while lamp 109 indicates the row or shelf on which the defective switch is located. It should be noted also that, while such a switch is stuck and until it is completely released, ground from ofli-normal contacts l) is maintained on bank contact, as 42D, in bank 25 of the idle position locator X, to prevent this switch from being selected for an inward call while it is in trouble.

In case the called subscribers station V is busy, the 3) bank terminal will be grounded through contacts C of relay 51 in the finderconnector switch in connection with that station. Hence, when, before the release of relay 48, the switch wipers P, L and T come to rest on the bank terminals associated with station V, a circuit is closed from ground at the p bank terminal through the P wiper, contacts C of relay 48, winding of relay to battery.- Relay 50 then operates and remains looked over a circuit whichextends from battery through the windingofrelay 50, make-before-bre'ak contacts E of relay 48, contacts B of relay 50, contacts C of relay 45 to ground. Under these conditions, a circuit is closed for operating relay 52 which may be traced from ground through contacts C of relay 50, contacts A of relay 48, winding of relay 52 to battery. Relay 52 then operates, closing at its Dcontacts a circuit which shunts the high resistance winding of relay 44, thus increasing the current in the dial lead circuit 102 and thereby lighting the busy lamp 66 at operators position Z.

The circuit changes effected by the operation of relay 52, other than the shunting of the upper winding of relay 44, aroetiective in controlling the operation of the busy position. locator Y, which operation will now be described. As previously mentioned, it is the function of the busy position locator Y to respond whenever a called line is found busy, to set up a localcircuit to the calling operators set, and to send over this circuit signals which cause the operators printer to record the position number of the operator who is connected to the busy line. At the nine time alamp, as 63 (Fig.2), is lighted at the central station operators set in connection with the busy line, thereby indicating to this operator that the connection is not to be released since a message is tobe re routed ior transmission to the connected subscribers station. i

Only the switch W is shown in the drawings. As previously mentioned, however, the banks of other switches in the same group with d are inultipled thereto by conductors 13, 16 and 17. In the switch in connection with the busy subscribers station, the relay,

as 53, is connected through contacts F of WVhen relay 52 of switch W operates, the busy lamp at set Z is lighted over a circuit that may be traced from battery, low resistance winding of pulsing relay 44 (the high resistance. winding being shunted), contacts 1) of-reiay 52, dial lead 102, busy lamp 66,

dial contacts of switching relay to ground at release key 64; and ground is removed from the corresponding bank terminal C of the busy position locator switch Y while ground is connected to the start-lead 111 which is multipled to the relays, as 52, in all of the combination switches in the same group. Ground on the start-lead completes a circuit through the winding of relays 7? and? 5. This circuit may be traced from battery, winding of relay Tl, contacts E of relay 76, winding of relay 75, start-lead 111 to ground on contacts E of relay 52 or switch W. Relay 77 operates, closing an obvious circuit for control relay 78 which, in turn, pulls up,starting the motor 82which drives the cainfor controlling the distributor contacts 83-94; Relay operates and estab lishes a circuit from battery through the switchstepping magnet 74, contacts of this terminals corresponding to a. finder-connector switch that is either idle or connected through to a station line in the normal working condition, a circuit is extended from ground through the contacts F of a relay, as 52, in this switch, through a contact interminal bank 69 and wiper 72 to the busy position locator stepping magnet 74. The stepping magnet then operates, breaking its own circuit and releasing, thus advancing the rotary switch Y1 one step. If the wiper now finds ground on the next contact in banhterminal 69,the steppin g magnet circuit will again be closed, causing the rotary switch Y1 to advance one more step. o This action continues and the switch steps around untii the wiper 72 reaches an ungrounded contact, asl'OC, in terminal bank 69. This ungrounded contact corresponds to the finder-connector switch )V in which the relay 52 is operated. It should be noted, however, that if two central. station operators dial busy lines at about the same time, a relay, as 52, will be operated in two combination switches and the rotary switch Y1 will stop when 3 the wiper 7 2 reaches the contacts in terminal bank 69 connected to the first of these two switches. In this case, one of the two operators will not receive the busy position locator signal immediately, but must The resistance of Wait until the other operator releases the circuit.

As soon as the wiper 72 associated with bank 69 reaches terminal 70C which is not grounded, relay 76 operates since its winding is no longer shunted, while stepping magnet 74 fails to operate. Operation of relay 76 opens at its E contacts the circuit to the windin g of relay 75 and to the windingof relay 7 7. Relay 75 now releases, opening the circuit of stepping magnet 74, but relay 7 7 being slowreleasing, remains energized until relay 76 at its C contacts closes a locking circuit for itself which extends to battery through another winding of relay 77. Relay 76 at its 1) contacts also connects battery through a winding of relay 77 to the wiper 71 associated with terminal bank 68 and thence through contacts 70B, contacts B of relay 52, contacts G of relay 51 in switch V7, T wiper and bank terminal t, thence over conductor 17 to the 2? bank terminals of all other finder-connector switches. The relay corresponding to relay 51 of switch W in the busy switch, which is-in connection with the called line, is operated, so that the circuit just traced extends through the 6 bank terminal and Wiper T of this busy switch, contacts F of the relay corresponding to relay 51, winding of relay 53 to ground. Relay 53 of the busy switch then operates.

Operation of this relay extends ground over three circuits as follows:

(1) Contacts C of relay 53, winding of the hold relay at the connected operators set, corresponding to relay 62 of the set Z, and to battery;

(2) Contacts B of relay 53 to a terminal, as 136, of the units code relay group;

(3) Contacts A of relay 53 to a terminal, as 136, of the tens code relay group.

The termination of circuits (2) and is such that relays of the tens code group Y2 and of the units code group (not shown) are operated to set up five-unit signal combinations corresponding to the tens digit and,

the units digit, by which this busy finderconnector switch and its associated operators position are designated. The circuit traced to the hold relay, corresponding to relay 62, of the busy operators set causes this relay to operate and lock itself to ground through the release key corresponding to key 64. This circuit also extends through the hold lamp corresponding to lamp 63 at this position and to battery. The hold lamp lights, informing the busy operator that the connection is to be held for an additional outgoing message.

As previously mentioned, the motor 82 was started when the relay 78 was operated. When the wiper 70 comes to rest on contact 7 0a, which is in connection with switch W, a circuit is completed for operating polar relay 79 which may be traced from positive battery, winding of polar relay 57 (Fig. 2), contacts C of key 54 (which was restored when the operator noticed the lighted busy lamp), transmitter contacts 56, contacts B of switching relay 55, conductor 106, contacts C of relay 52' (Fig. 1), contacts 70A (Fig. A) wiper 70, contacts B of relay 76, winding of relay 79, conductor 101, to ground on contacts A of relay 82. Relay 79, therefore, operates,

preparing a circuit for relay 80. Upon the first closure of contacts 83 of the distributor by the cam (not shown) relay 80 is operated over a circuit from battery, winding of re lay 80, contacts B of relay 81, contacts of polar relay 79, to ground on contacts 83. Relay 80 locks through its locking contacts, winding of relay 81 to ground on contacts A of relay 76. When cam operated contacts 83 open, removing the short circuit from across its winding, relay 81 operates. The operation of relay 81 prepares an operating circuit for relay 82. Upon the second closure and opening of distributor contacts 83, relay 82 operates over a circuit from battery, winding of relay 82, contacts A of relay 81, contacts of polar relay 7 9, to ground on contacts A of relay 76. The cams controlling the distributor contacts 839 lhave, therefore, made at least one complete revolution and the motor 82 is now running at operating speed. The operation of relay 82 opens at its A contacts the shunt around the circuits controlled jointly by the code relays and the distributor contacts, so that the operators printer at set Z is now under control of these circuits.

As the cams (not shown) driven by the mo tor 82 revolve, contact 83 closes momentarily once per revolution, but relay 82 is locked, the contacts 83 have no effect. The remaining contacts 84149401 the distributor close in a sequence such that, during one revolution, a figure shift signal, a dash signal, and a two digit number which corresponds to the code relay set-up, are sent out over the line 101.

The cam which controls the figure shift contacts 84 is so cut that these contacts will transmit, first, a figure shift signal and a dash signal, and then, during the remainder of the revolution, will close to provide two stop pulses, one for the tens digit signal and the other for the units digit signal. The five pulses of the tens signal are controlled by successive closures of the contacts 85-89, and the character of these pulses (whether marking or spacing) is controlled by the contacts of the tens code relays 95-100 inclusive. The five pulses of the units signal are controlled by successive closures of the contacts ,94, while the character of these pulses is controlled by the contacts of the six units code relays (not shown), which are arranged similarly to the siX tens code relays -100.

As the cams (not shown) revolve a series Ell of impulses will be sent over the line which will cause the calling operators set printer to shift to the figure position and to print a dash followed by a two digit number which vill correspond to the code. combinations set up on the tons and units code relay groups. Since the setting of these code relay groups has been controlled by the relay corresponding to relay 53 in the busy switch in connectionwith the called line, and since this switch is individual to a particular operators position, the number which the distribute-r sends back to the calling operator will indicate the position number of the operator in connection with the called subscribers station. it is to be noted. that the units group of code relays cooperate with dis tributor contacts 90 9 1 to send the units digit signals over conouctor 1 10 and thence over conductor 101 to the operatcrs printer at set Z. The calling operator at Z notes this number on the message blank and then operates the release key 6 1. i

The operation of the release lrey restores to normal, in the manner previously described, the circuits and mechanism of the combination switch W. relay releases upon the operation of the rel-ease key, negative battery is applied through contact A of relay 55 (Fig. 2) to the previously traced circuit or". the polar relay 7 9, with the result that the contact of that relay isopened. Belay 50 releases when its circuit is opened at contact 0 of relay 415, and relay 5() in turn opens the circuit of re lay 52at contact C of relay 50. When relay 52 releases it opens at its B contacts one winding of relay 7 7; at its C contacts the section of the line circuit between 106 and 101;

' at itsD contacts the shunt around the high resistance winding cl relay 14; at its E contacts the start-lead 111 for the busy pos1- tion locator; and at its F contacts, connects ground to contact 700 in terminalbank 69, thereby causing relay "76 to release since both terminals of its winding are grounded. Upon releasing, relay 76 at its contacts A opens the locking circuits of relays 80and 82 and the operating circuit of relay 81; at its (l contacts opens the other winding of relay 77 which releases after an interval; and at its E contacts reconnects relays 77 and 75to the start-lead 111. The release of relay 77 and the consequent release of relay 7 8 re opens the operating circuit of motor 82, stopping the rotation of the cams (not shown). It isto be notedthat the relay 7 7 is a slow-release relay. This is to prevent the motor 82 from stopping before the busy position locator has time to respond to another busy call, if such a call should be waiting. 1 The release of relay 82 reconnects ground, at its A contacts, to conductor 101, and the release of the other relays mentioned prepares the busy position locator to-answer the next When the switching chart gives the number to be sent to the call ing operators printer. This number corresponds to the terminal connection of the leads from contact A of the relay in the busy switch corresponding to relay 53 in switch W. The second column gives the code relay terminal grounded by relay 53 of switch W.

The third column shows the tens code relays that are operated, and the fourth column shows the circuits set up to the distributor contacts which correspond to the five unit printer code signal of the number to be sent.

('lIcnts Terminialg igi s grounds y I Distributor contact to be relay 53 of Code mass Operated connections closed sent switch W 1 i 130 (1) 95,96,100 (1) 85, 86, S7, 89 2 136 (2) 98,100,95 (2) 85,86, 89 3 131 (3) 95 (3) 85 4 138 (4) 99, 98 (4) 86. 88 5 139 (5) 10 (5) 89 6 135 (6) 97, 100, 95 ((5) 85,537,559 7 133 (7) 96,95 (7) 85, S6, 87 8 134 (8) 97,98 (8) 86,87 9 137 (9) 99,100 (9) 88,89 0 132 (0) 96,100 (0) 86, 87, 89

Similarly, to send corresponding units digits, similarly related units code relays would be operated, similarly related termi na-ls, as 136, would be grounded by relay 53 of switch W, and similarly related distributor contacts in the group -94 inclusive would be grounded; and circuits thus prepared to operate the calling operators printer to print the units number.

Alternative management for 10/2714) bum-7c z'ndwatzon In Fig. 5 is shown an alternative arrangement whereby a visual indication, rather than a printed record, of the number of the busy operators position is given by means of a bank of signal lamps. These signal lamps comprise a tens bank 146 and a units bank 147. A pair of lamps, one 1 18 in bank 146 and another 149 in bank 147, is controlled by relay 53 in switch W. Similarly, the relays corresponding to relay 53 in each of the other switches control a pair of lamps, one in bank 146 and the other in bank 147. Upon the operation of relay 53 in switch W, lamps 148 and 149 are lighted, indicating to the operator who has called a subscribers line in connection with set Z that the latter set is connected with the busy line. Similarly whenever an operator calls a line in connection with one of the other switches, the relay corresponding to relay 53 in that switch is operated, and a pair of lamps, as 150 and 151, are thereby lighted, indicating to the calling operator that the set associated with the busy switch is in connection with the called line. It is to be noted that the lamp bank is common to the operators sets, and is so positioned that it is visible to any of the operators at these sets.

In addition, a multiple connection to the hold relay and hold lamp at each operators set, as Z, is placed under control of either relay 52 or 53 in the associated combination switch 1V. Consequently, the hold lamps 63 at both the calling and the busy operators sets are lighted. This arrangement is nec essary to take care of the situation when more than one central station operator has called a busy subscribers line. As previously explained, the busy position locator is then associated with the calling switches one after another, and as a result different num bers, corresponding to the different busy sets are flashed on the lamp bank. Conse quently, means must be provided to enable a calling operator to distinguish from the numbers flashed, the number designating the busy set connected to the subscribers line that he has called.

In the drawings, the relays 52 and 53 are shown connected for operating the busy position locator Y and the lamp banks 146 and 147. The manner in which these relays are connected with the circuits ofthe switch W is indicated in the description to follow and may be traced by reference to Fig. 1. It is to he noted that in 5, parts similar to those in Fig. 1 are designated by the same reference characters.

Assume that an operator. such as Z, has dialled a busy line, as 1. Under these conditions relay 52 of switch lV operates over a circuit from battery, winding of relay 52, conductor 116, contacts A of relay 48 (see Fig. 1), to ground at contacts O of relay 50. Upon operating, relay 52 its A contact opens the connection from contact 42A in bank 22 of locator X over conductor 144, contact A of relay 52, conductor 115 to the test wiper T of switch W: at its B contact connects the test wiper T of switch WV to contact 7 0B in bank 68: at its O contact connects conductor 143, which extends in series through the hold relay 62 and the lamp 63 at operators set Z, to contact 76a in bank 67; at its D contacts completes a shunt circuit over conductors 102 and 142 around the high. resistance winding of pulsing relay 44 in switch V, thereby lighting he busy lamp 66 at set Z in a manner eviously described;

at its E contact rounds the start-lead 111 which is multipled by conductor 145 to other relays, as 52, in the other switches;

.and at F removes ground from contact 700 corresponding to switch W in bank 69 of the busy position locator Y.

Ground on the start-lead operates relay over an obvious ircuit. Operation of relay 75 establishes a circuit from battery through the winding and contacts of the rotary magnet 7 4, contacts of relay 75, thence over two parallel circuits, one extending to the wiper 7 2 associated with terminal bank 69 and the other extending to ground through the winding of relay 76. If the busy position locator switch is not resting on terminals associated with a switch that has tested a busy subscribers line, the circuit traced to the wiper 72 associated with terminal bank 69 extends to ground through the terminal contact. Under these conditions relay 76 is short-circuited and does not operate, but the rotary magnet 74 does, thereafter opening its own circuit and releasing, to advance the wipers 7 072 of the switch one step.

This action will continue until the wipers of the busy position locator switch reach the ban; terminals associated with the calling finder-connector switch W. At this time, as previously explained, the rotary magnet 74 and the relay 7 6 are connected in series, but only relay 76 operates, looking through its own contacts. The wipers of the switch, therefore, remain in contact with terminals associated with the switch W. Operation of relay 7 6 opens the circuit through the winding of relay 75, allowing this relay to release andopen thecircuit of the rotary magnet 74. Relay 76 also connects battery to a circuit extending through the wiper 71 associated with bank terminal 68 of the busy position locator Y, contactsB of relay 52, conductor 115, contacts G of relay 51 (see Fig. 1) of the calling switch V7, T wiper and 6 bank terminal of this switch, thence over the multipled bank wiring, .25 bank terminal and T wiper of the busy switch, contacts F of relay in this switch corresponding to relay 51 in switch W, conductor 114, winding of the relay, which corresponds to relay 53 in switch W, to ground. The relay in this busy switch, corresponding to relay 53 of switch l/V, operates over this circuit.

Operation of relay 76 also establishes a circuit from ground through contacts A of relay 76, wiper 70 associated with bank terminal 67 of the busy position locator switch, contacts O of relay 52 of the calling finder-cone nector switch conductor 143, and in parallel through the winding of hold relay 62 and through the hold lamp 63 (see Fig. 2) of the calling operators set Z. The hold relay locks to ground through the release key 64, and the hold lamp 63 lights to inform the operator to watch the lamp bank indicator for the number of the busy operators position which is in connection with the called line.

It is to be noted that contact 0 of the relay 53 andthe armature associated with contact Got relay 52 in each combination switch are multipled to conductor 143, which is connected in multiple through the hold relay 62 and the holding lamp68 at the associated operators sets. Consequently, when the switch W is a calling switch and relay 52 is operated, the lighting of the holding lamp informs the calling operatorto watchthe lamp bank, and when the switch W is. a busy switch and relay 53 is operated, the lighting of the holding lamp informs the busy operator that the connection is to be held until a re-routed message for the connected subscriber is received. b

At the time of the operation of the relay of the busy finder-connector switch, corresponding to relay 53. of switch W, three circuits were closed as follows:

(1) From ground through contacts C of the relay corresponding to relay 53 and in parallel throughthe winding of the hold relay 62 andthrough the hold lamp 63 of the operators set which is in connection with the called lines; p From ground through contacts B of thisirelay to a lamp 148 in the tens row 146, which correspondsto the tens digit by which this operators set is identified;

From ground through contacts A of thisrelay to a lamp 1&9 in the units row 147,

' ugly.

which corresponds to the units digit of the number by which this operators set is identified.

Operation of thehold lamp 63 just described will inform the operator in connection with the busy subscribers line that another message to be sent and that the station is not to be released. he two lamps 148 and 1&9 ofthe lamp bank unit light-to indicate to the calling operator the number oi the position which is in connection with the called line. a The operator, upon noting ths numbciy rc-routes the message accord- 'lhe calling operator then operates the release key 64; (Fig. 1) to restore the calling finder-connector switch W to normal. Belay 52 01. this switch releases, transferring ground from the start-lead ill to the corresponding bank terminal 700 of the busy position lccator switch. This ground will extend through the wiper "72 associated with term? bank 69 to shunt the winding of relay 7 Relay 76 thereupon releases, re-

xto'ring, in the manner previously described, the circuits ot the busy position locator Y to normal. It another busy call is waiting, relay operates immediately and the busy position locator Y responds to this call, but it there are no busy calls waiting, the wipers of the busy pos tion locator switch remain on the bank terminals last used.

it should be noted that the number displayed bythe lamp indicators 14:6 andla'l at any time will be the number of the position in connection with the busy line which is wanted by the calling operator. This lamp bank may be common to a fairly large group of operators, several of whom may dial busy lines at the sametime. To

avoid confusion of busy position numbers Inward service To establish a connection fromthe subscribers station set V to a central oflice operator, such as Z, the calling key 7 (Fig. 1) at the station V is operated. This action shunts out the high resistance winding of the polar line relay 2 at station V, and increases the line current from the idle condition value to a value sufficient to operate marginal line relay 10. Contact A of line relay 10 is wired to all t bank terminals corresponding to this station number, while contact B of this relay is wired to the winding of a group relay 20 which is associated with the particular switch level in which the calling line is located. The

proper t bank terminal in all of the switches,

such as W, to begrounded and theproper group relay, such as relay 20, to be operated. Operation of group relay 20 connects ground to a terminal 0 of the vertical commutator corresponding to the level in which the terminal contacts of the calling line appear. Group relay 20 also connects ground to contacts of chain relay 21 to control the starting of the idle position selector.

As previously. stated, it is preferable in large installations to provide more than one idle position selector in order to avoid excessive wear on the wipers of the selector, which might occur if a single switch had. to rotate over the terminals associated with a large number of operators sets. In such an installation it is possible that all of the operators sets associated with one idle position selector might be busy at the same time. In a responding relay in each of the other switches in this particular group. A chain. relay, as 21, is similarly associated with each addi- One chain relay, as 21, is astional group of switches and each additional idle position locator. It is obvious that, as long as one or more switches of a group, as switch 1V, are idle, the associated chain relay, 5 as 21, will be operated, but that, as soon as all switches of this group are busy, the chain relay, as 21, will release. Release of the chain relay, as 21, switches the start-lead circuit 11'!" to the next idle position selector (not sh own) so that one of the operators sets of the second group will receive the next incoming call.

Assuming that some of the switches asso- Z ciated with the first idle position selector X 15 are idle, the corresponding chain relay 21 will be operated as shown, and the start-lead 117 will be extended through the winding of relay 129, contacts B of chain relay 21, to the idle position locator X and thence through 29 contacts A. of relay 44, winding of relay 45, wiper 28 associated with terminal bank 22 of the rotary switch X1, home contact 34, winding of relay 38 to battery. Relays 129, 45 '"s and 38 operate over the circuit just traced. 25 The closure of contacts C of relay 38 connects the winding of this relay directly through contacts A of relay 44 to the startlead' 117, so that relay 38 is held operated "7: independently of the wiper 28 associated with 3 terminal bank 22. This action also short circuits the winding of relay 4?, which re leases, its operation serving no useful purpose at this time. The closure of contacts B i of relay 38 establishes a circuit from ground through the lower or low resistance winding of relay 39, contacts 13 of relay .38, upper or high resistance winding of relay 39, to battery. Relay 39 operates, establishing a circuit through winding of the rotary mag- 40 net 40 and rotary magnet contacts 118, contacts A of relay 39, thence in parallel through the winding of relay 43 to ground, and through contacts B of relay 43, wiper 31, to grounded home contact 36. The rotary 45 magnet 40 now operates, opening its own contacts 118 and releasing to step the switch X1 one step. The wiper 31 associated with terminal bank 25 comes in contact with the bank j terminal which is associated with the num her one tinder-connector switch of this group.

If this switch is busy its relay corresponding to relay 45 of switch l/V is operated, extending ground to this bank terminal, and the stepping magnet 40 accordingly again operates and releases to step the idle position locator switch X1 one'more step. The idle position locator switch X1 steps around in this manner until the wiper associated ..with terminal bank 25 comes in contact with 0 .111 ungrounded bank terminal, i. e., one corresponding to an idle finder-connector switch. hen this occurs the circuit thr ugh the rotary magnet 40 extends to 'I ground through the winding of relay 43. 55 The relay 43 operates but, because of the circuit resistance, the rotary magnet 40 does not receive enough current to operate, and, therefore, the wipers 2833 come to rest on terminals associated with the lowest numbered finder-connector switch that is idle. It will be assumed that this is switch W.

Operation of relay 43 connects ground through its A contacts, wiper 30 associated with terminal bank 24, terminal contact 420, windings of relay 44 of switch W in series and to battery. This ground also closes a circuit extending over the dial lead 102 and through the busy lamp 66 and switching relay 55 of the associated operators set Z to battery. The switching relay 55 thereupon operates, locking up through the release key 64, thus closing a circuit for lighting the guard lamp 58 and applying an additional ground to the dial lead 102. Relay 44 operates, closing an obvious circuit through the winding of relay 45. Relay 45 thereupon operates, closing a circuit from ground through its contacts E, bank terminal 421) and associated wiper 31 of the idle position locator switch X1, contacts C of relay 43, winding of relay 44 to battery. Relay 44 operates, establishing a circuit from battery through the winding of relay 45, contacts C of relay 44, wiper 29 associated wit-l1 terminal bank 23, bank terminal 42B of the idle position selector switch X1, in series through so-called interrupter contacts associated with the vertical magnet 19 and rotary magnet 18 of the selected finder-connector switch W and to ground. Relay 45 operates over the circuit ust traced. At the time that relay 44 operated, relay 38 was released by the opening of contacts A of relay 44, so that a circuit may now be traced from ground through the lower or low resistance winding of relay 39, contacts A of relay 38, contacts of relay 45. contacts D of relay 43, wiper 32 associated with terminal bank 26, contacts H of relay 51, contacts B of relay 45, eleventh rotary contacts 12, off-normal contacts B, winding of relay 46, winding of vertical magnet 19 and to battery. The vertical magnet 19, relay 46 and relay 39 operate over the circuit traced.

The operation of the vertical magnet 19 opens at the interrupter contacts mentioned above the circuit of relay 45 which, therefore, releases, opening the circuit through relays 39 and 46 and the vertical magnet 19. Both relays 39 and 46 are slow-release relays and do not release at this time, but the vertical magnet 19 does release, reclosing the interrupter contacts, and thereby re-energizing the relay 45. The relay 45, upon reenergizing, closes the previously traced circuit for the vertical magnet 19. When the vertical magnet was operated it caused the switch W to take one vertical step, thereby operating the off-normal contacts 47. V7 hen the relay 46 operates a circuit is prepared a rarian for subsequentlyoperating relay 38. This c1 rcuit may be traced from battery, winding of relay 88 contacts B of relay 44-, winding of relay wiper 28, contact 42A, contacts C ofrelay 46to the wiper R co-operating with the vertical commutator. The oilnormal contacts and relay 4-6 are now operated so that the pulsingcircuit to the vertical magnet 19 extends through the off-normal contacts A through contacts B of relay 46, winding of relay 46; winding of vertical mag- 1 net 19 to battery.

As stat-ed above, the operating circuit fOl' the-vertical magnet isagain closed, and upon the energization of the vertical magnet the interrupter contacts are again opened releasi relay 45" and reopening the vertical magnet circuit. This reciprocalaction between the vertical magnet 19 and the relay 45 of the idle position selector X causes the vertical magnet circuit to be alternately opened and closed thus stepping the finder-connectorswitch WV vertically. As the switch steps vertically the vertical wiper R 1 vertical steppingof the switch.

operates and at its A contacts opens the ground circuit to the relay 46 and the ver is carried over the terminals, as r, of the vlflywinding of relay 4.5, contacts B of relay as 44:, winding of relay 38 tobattery. Relay 45" is-held energised to prevent any further tical magnet 19. The relay 38 at its B contacts closes a local holding circuit through the windings of relay 39; i

The finder-connector switclrVV consequentlycomesto rest with itswipers advanced to the level: of the bank terminals of the calling line and after a short interval of timeyrelay 46: releases. Release oi this relay opens the circuit from th vertical-wiper R associated with. the vertical commutator to the winding" )f relay 38,. thus releasing relay 38.1 Release of relay 38- establishes a pulsing circuit through the loweror low resistance winding 0t relay 89, contacts A of relay 38,.contacts of relay 45, contacts D of relay 43', wiper 32 and terminal bank 265 contacts H of relay 51,

- contactsB of rel'ayu4t5, eleventh notary contacts 12, operated cit-normal contacts Aycontacts A of relay 46,. contacts D of relay 50 and in paralleli through the rotary 1nagnet18- 1nd: the winding of slow-release relay 4:8" to battery.. The rotary magnet 18 thereupon operates causing the switch shaft and wipers to take one rotary step andopening-the rotary interrupter[contacts The circuit tothe winding on relay 4'5, whichwas closed upon Relay 38 a the release of the vertical magnet 19, is now open at the rotary magnetcontacts and: this relay releases opening the circuit to the rotary magnet 18 and relay 48 of the finderconnector switch W. The rotary magnet 18 then releases closing its contacts, but sincerelay 4-8 of the finder-connector switch W isiof the slow-release typeit remains operated. Closure of the rotary magnet contactsagain establ shes a circuit through'the widingof relay 45 and this relay again operates to energize the rotary magnet 18 and the relay 48 of the finder-connector switch.

This action continues until the Wipers of the linder connector switch WV are steppedaround to the bankterminals associated with: the calling line. When these bank terminals are reached, circuit is closed from ground through contacts A of line relay 10, t bank terminal and wiper T contacts Gr of relay 51, contacts A of relay 52, bank terminal contact 12A; wiper 28 ofthe idle position selector switch X1 winding of relay 4E5, contacts B of relay 44, winding of relay 38 tobattery. Relay 38 then operates opening the circuit previously traced throughits A contacts to the windings ofthe rotary magnet 18 and re lay 48 so that the finder-connector switch W comes to rest on the bankterminals of the calling line 1.

After a short interval relay 4-8 of the finder connector switch releases closing a circuit from battery through the winding of cut-oil relay 11;, 7) bank terminal, wiper P, contacts B ot relay 48, lower winding of relay 51, con tacts A of relay 50, contactsC of relay 45 to ground. Cutoff relay 11 then operates while relay 51 also operatesbut closes at first only its D contacts. relay 51 energizes the upper or high resistance winding, thus operating the remaining contacts of relay 51.

The following circuit changes are eflected by the operationoi relay 51 (1) The openingof itsA contacts opens a circuit which has extended from ground on contacts D of relay l5 through contacts A of relay 51-, winding of dash-pot relay 104 to battery; 1

(2) The opening of its B contacts opens a circuit from ground through the winding of the chain relay 21 7 (3) The closure of its C contacts connects ground to the P wiper andthence through the winding of cut-off relay 11 to hold that relay operated and to make the line 1 busy to other calls; 1

(A) The closure of its D contacts closes a V circuit through the high resistance winding 1 of relay 51, as previously described;

( 5) The closure of its E contacts connects Closure of the D contacts of 

